Technical Field
The technology relates to methods and structures for forming semi-nitrogen-polar and semi-gallium-polar III-nitride layers and devices on sapphire substrates.
Discussion of the Related Art
Gallium nitride (GaN) and other III-nitride materials are widely recognized as desirable materials for fabrication of integrated devices. These materials typically have wider band gaps than silicon-based semiconductors and can be used to make electro-optical devices (e.g., LEDs and diode lasers) that emit radiation in the green and blue regions of the visible spectrum. Also, because of their wide band-gap, III-nitride materials can exhibit higher breakdown voltages when used for fabricating integrated transistors, making these materials attractive for high-power electronics.
Like silicon, III-nitride materials may be grown as high-purity, crystalline material. Unlike silicon, III-nitride materials are typically more difficult and expensive to grow than silicon, so that bulk substrates of III-nitride materials are not currently as commercially feasible as bulk silicon substrates. As a result, researchers have developed, and continue to develop, methods for epitaxially growing integrated-circuit-grade III-nitride layers on silicon or other crystalline substrates. Once grown, integrated devices may be fabricated in the III-nitride epitaxial layers using planar microfabrication techniques.